Data processing devices are arranged in networks or are connected to networks so that information (data) can be interchanged between the data processing devices in the networks. Computers, PDAs, servers, printers, gateways, and other data processing devices have at least one processor, memory and at least one data interface. The data processing devices (computers, PDAs, servers, printers, gateways, etc.), including the communication components (telephones, VoIP telephones, searching systems, etc.) in the form of data processing devices, have a respective unique address, these addresses being able to be used by each network element (data processing device) to interchange information with another network element in the same network.
Networks frequently contain, besides the data processing devices, central services which are often also called “servers” or are installed on “servers”, the central services being used by applications which are installed on the individual data processing devices. In this context, information is interchanged between a central service of this kind and an application which uses the central service. Normally, one and the same central service is available to a plurality of applications and hence a plurality of data processing devices for use, for example an e-mail server produced as a central service stores and conveys all electronic messages (e-mails, etc.) which are interchanged by the applications (in this case these are e-mail programs) on the connected data processing devices.
A special case of the networks described is what are known as “ad-hoc networks”, where the data processing devices arranged in an ad-hoc network frequently change. An example of an ad-hoc network of this kind is what are known as “WLAN hotspots”, in which all data processing devices which are situated within the radio range of the transmission/reception device can be part of the ad-hoc network. Data processing devices, particularly those with a wireless connection for data transmission, may even form an ad-hoc network without a central infrastructure (“hotspot”) as soon as at least two data processing devices connect to one another and can interchange information. Another example of ad-hoc networks is what are known as “peer-to-peer networks”, in which some (at least two) data processing devices in a network of any size (e.g. the internet) enter into a logical relationship with one another. Peer-to-peer networks of this kind are frequently used for file interchange, for example, or else for voice data communication (“VoIP telephony”), without using a circuit-switched network (telephone network) to do so.